There are many prior art devices available which alter the tonal quality of electrical audio signals. For example, one prior art device has a distortion generator or a distortion compressor stage followed by a filter with a roll-off or attenuation with increased frequency, along with means to adjust either the amount (steepness) of the roll-off, or the point (knee) of the roll-off. However, the filter in such a device is very crude. Further the adjustment means requires the operator to experiment with different settings or combinations of settings in order to define a desirable sound, and even then the device is limited in the quality of sound which it is capable of producing. Moreover, the arrangement just described does little if anything to tailor or enhance the character or quality of the tone of the signal produced by the distortion generator or compressor stage.
Many prior art devices are available for electrically introducing reverberation effects into an audio electrical signal. Many of these devices are susceptible to mechanical jarring, and produce "Boing" type sounds when subject to such jarring or mechanical vibration and from short transient sounds. At least one prior art reverb unit incorporates a multiple output bucket brigade device, i.e. analog shift register. However, for certain applications this device does not provide sufficient delay of the inputted signal, produces undesireable echo with pulse inputs, and is limited in the type and quality of the reverb that it provides.